Tissues

Levels of Organization

• The human body has several levels of organization:

• Cells of the same type joined together are called TISSUES

• Different Tissues are joined together to form ORGANS

• Various organs are arranged into an ORGAN SYSTEM

Essential Terms

tissue• group of similar cells that function together

to carry out specialized activities and usually have a common embryonic origin

histology• science that deals with the study of tissuespathologist• physician who specializes in laboratory

studies of cells and tissues for changes that might indicate disease

Introduction1. While cells are basic functional and

structural unit of life, they function in groups as tissues to carry out specialized activities

2. Properties of tissues are influenced by factors such as extracellular material and connections between cells

3. Tissues may be hard, semisolid, or liquid

4. Vary with kind of cells present, cellular arrangement, and types of fibers present

Human Body Tissues

Classified into four groups according to

– function

– structure

Groups

1. epithelial

2. connective

3. muscle

4. nervous

EPITHELIAL TISSUES: covers body, lines cavities

• covers entire body surface and most of the body's inner cavities.

• outer epidermis (skin) protects from injury and drying out

• inner epidermal tissue, on internal surfaces protects, secretes mucus (e.g. along digestive tract)

CONNECTIVE TISSUE

• : connects organs

• Functions• bind

structures together

• fill up spaces• provide

support and protection

• store fat

Types of Connective Tissue:

• 1. Loose: join tissues, hold organs in place, fat storage

Fibrous

• bundles of collagen fibers, very strong. Used in tendons (connect muscle to bone) and ligaments (connect bones to other joints.

Cartilage

• has flexible matrix rich in protein and fibers. e.g. nose, ears, vertebrae, ends of bones.

Bone:

• rigid connective tissue. Matrix of calcium salts.

Blood

• 5. matrix is liquid called plasma.

Muscle Tissue Contracts for Movement

• muscle tissue is composed of fibers made of actin and myosin proteins (among other “helper” proteins) whose interaction is responsible for movement.

There are 3 Distinct Types:

•Striated

•Involuntary

•Only in heart

•Striated

•Voluntary

•Attached to bone

•Non-striated

•Involuntary

•Walls of internal organs

Nervous TissueConduct Electrochemical

Messages• specialized tissue that forms nerves,

brain, spinal cord

• conduct electrical & chemical messages along special cells called neurons. Composed of cell body, dendrites (conduct messages to cell body), axon (send messages away from cell body).

• axons and dendrites are nerve fibers. Bundles of nerve fibers are called nerves.

• Nerves conduct messages to and from spinal cord, brain, and sense organs to register sensation and trigger muscle movement.

Cell BodyAxon

Dendrite

Synaptic Endings

Structure of a Neuron (in this case, a motor neuron)

ORGANS: Tissues working together

• organs (e.g. the heart) are made up of one or more types of tissues (usually more).

• SKIN is also an example of an organ. It is your largest organ, and has several tissue layers.

• Skin covers body surfaces, gives protection from water loss and invasion by microorganisms, contains sense organs, helps to regulate body temperature Skin is made up of Three Layers.

• Epidermis: is outer layer. Composed of

• stratified squamous epithelial cells.

• Basal cells at base of this layer produce new cells.

• Pigment cells (melanocytes) here produce melanin, responsible for skin colour. Keratin protein hardens skin cells. (Hair & nails are made of tightly packed keratinized cells).

• Dermis: middle layer. Loose connective tissue with many elastic fibers. Sweat glands, nerve endings, blood vessels, and hair follicles located here.

• Subcutaneous Layer: bottom layer. Loose connective tissue containing adipose cells (fat!)

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Human Organ Systems

• each located in specific location, with specific functions. (e.g. digestive system).

• many internal organ systems enclosed within coelom, a cavity within the body.

• organ systems contribute to maintaining a stable internal environment (homeostasis). e.g. Temp, pH, [glucose], blood pressure.

1. Digestive convert food to usable nutrients

2. Circulatory transport of necessary molecules to cells

3. Immune defense against invading pathogens

4. Respiratory gas exchange

5. Excretory gets rid of metabolic wastes

6. Nervous & Sensory regulation and control, response to stimuli, processing information

7. Muscular & Skeletal support and movement

8. Hormonal regulation of internal environment, development

9. Reproductive producing offspring